A long long time ago, I theorized that it should be possible to run a big boilered machine without plumbing in, by removing the vacuum breaker and using the vacuum to let the boiler fill itself.

New Marcfi single-group espresso machine and grinder from 1996

Due to circumstances, I've been running my Faema Lambro like this for a few months now, and I must say, it is completely doable and the priority of plumbing in is just not there anymore. I turn the boiler on in advance, it runs on a timer. The boiler is very large compared to the water draw, so I only need to fill it once a day, and there will always be a time when I'm around and the boiler isn't pressurized. If not and the boiler is running low, turning it off, waiting for the boiler temperature to fall below boiling, filling, and getting back to temperature takes less than 15 minutes. This is usually not big of a deal. Honestly, I miss the plumbed drain line much more than the fill line.

So based on my experience, this should give those that want to run a big lever (or any big machine really) a bit more options in terms of placement. I hope this helps someone.

I do this all the time where I use a machine that is not on my main bench, without hooking it up to a water mains. I use the vacuum valve or wobbler weight (when applicable) while the machine is off to fill the boiler with water from my 5 gallon carboy with a funnel. When done I just hand tighten the vacuum valve/return the wobber weight and its pin to the fitting.

I'm not sure why it wasn't clear, but my process doesn't involve disassembly (which would be completely impractical for day to day use), but instead I submerge the hot water wand in a filled jug and open up the valve. The boiler then fills itself by suction. This way I don't introduce air into the boiler either so as long as my seals are good I don't get false pressure, so I don't miss the vacuum breaker either. The caveat is that this only works as long as the boiler pressure is lower than ambient, which is only possible if you don't have a vacuum breaker and the boiler is at negative pressure, ie, below 100deg C. In real life, I have not found this to be a big issue.

I'm more than happy to manually fill the boiler using an external rotary pump every couple of days, keeping the vac breaker in place and using the 'fill' knob